1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a method for manufacturing a thin-film transistor (TFT) substrate and a thin-film transistor substrate manufactured with the method.
2. The Related Arts
A thin-film transistor (TFT) has been widely used in electronic devices to serve as a switching device and a driving device. Specifically, the thin-film transistors can be formed on a glass substrate or a plastic substrate so that they are commonly used in the field of flat panel display devices, such as a liquid crystal display (LCD), an organic light-emitting display (OLED), and an electro-phoretic display (EPD).
Oxide semiconductors have a relatively high electron mobility (the electron mobility of oxide semiconductors >10 cm2/Vs, while the mobility of a-Si being only 0.5-0.8 cm2/Vs) and, compared to low temperature poly-silicon (LTPS), the oxide semiconductors have a simple manufacturing process, are highly compatible with a-Si manufacturing processes, are applicable to the fields of LCDs, OLEDs, and flexible displays, and are compatible to high generation manufacturing lines for applications to displays of large, medium, and small sizes, so as have a prosperous future of applications and be a hot spot of researches of the industry. Among the studies of the oxide semiconductors, InGaZnO (IGZO) semiconductors are the most developed one.
A thin-film transistor substrate comprises thin-film transistors and pixel electrodes. For a conventional oxide semiconductor thin-film transistor substrate, as shown in FIG. 1, after an oxide semiconductor layer 100 has been formed, a metal source/drain electrode 200 must be formed. The metal source/drain electrode 200 uses a wet etching process, which often uses strong acids and mixtures thereof (such as HNO3/H3PO4/CH3COOH) that readily cause damages of the oxide semiconductor of a back channel etching site. Using a dry etching process instead, however, causes problems of poor uniformity of etching. To dissolve such a problem, the known techniques often form an etch-stop layer (ESL) 300 after the formation of the oxide semiconductor layer 100 and before the formation of the metal source/drain electrode 200 in order to protect the oxide semiconductor layer of the back channel etching site for preventing damage caused in the processes of for example etching of metal source/drain electrode 200. However, forming the additional etch-stop layer requires an additional photolithographic process. The photolithographic process comprises various operations, such as film forming, exposure, development, etching, and peeling, so that forming such an additional etch-stop layer would greatly increase the manufacture cost and lower down yield rate.